How do tsunamis occur? Causes of tsunamis: signs of occurrence and danger of tsunamis

18.07.2018 20:16 1627

A tsunami is a wave that reaches very large sizes. It appears far out in the ocean and moves towards the shore at high speed. The word tsunami means "harbour wave" in Japanese. The Japanese name appeared because Japan suffers most often from this natural phenomenon.

There are several reasons for the occurrence of these terrible and dangerous waves. Most often, a tsunami occurs as a result of underwater earthquakes. At the same time, the water level rises sharply due to the displacement of the seabed. Unlike ordinary waves, when a tsunami occurs, the entire water column is involved, and not just the surface of the sea.

In addition to underwater earthquakes, tsunamis can cause landslides and underwater volcanic eruptions.

The incident that resulted in a tsunami due to a landslide occurred in Alaska in 1958. Huge masses of earth and ice fell into the water from a great height. As a result, a giant wave was formed, the height of which reached 500 meters off the coast!

When an underwater volcano erupts, an explosion occurs, which also contributes to the vibration of water and the formation of large waves.

If you guys lightly touch a glass or bucket filled with water, you will see small ripples form on the surface of the water. The same effect occurs when a tsunami appears, only the wave strength is much greater.

The tsunami moves at speeds from 50 to 1000 km/h. Its height can reach 50 meters or more! The closer the wave gets to the shore, the bigger it becomes. This is due to the fact that the depth is shallower near the shore. The consequences of this natural disaster are terrible. Tsunami waves hit coastal areas with terrible force and destroy everything in their path.

To combat the disaster, some countries, including Russia, have created tsunami warning services. They study the situation of seismic activity (earthquake danger) and if a tsunami occurs, they notify the population about it so that people can move away from the sea to a safe distance.

Most often, a tsunami occurs in the waters of the Pacific Ocean. Many underwater volcanoes are concentrated at its bottom and earthquakes occur in these places.

The distribution of tsunamis is usually associated with areas of strong earthquakes. It is subject to a clear geographical pattern, determined by the connection of seismic areas with areas of recent and modern mountain building processes.

It is known that most earthquakes are confined to those zones of the Earth within which the formation of mountain systems continues, especially young ones dating back to the modern geological era. The purest earthquakes occur in areas close to large mountain systems and depressions of seas and oceans.

In Fig. Figure 1 shows a diagram of folded mountain systems and areas of concentration of earthquake epicenters. This diagram clearly identifies two zones of the globe that are most prone to earthquakes. One of them occupies a latitudinal position and includes the Apennines, Alps, Carpathians, Caucasus, Kopet-Dag, Tien Shan, Pamir and Himalayas. Within this zone, a tsunami is observed on the coasts of the Mediterranean, Adriatic, Aegean, Black and Caspian seas and the northern part of the Indian Ocean. The other zone is located in the meridional direction and runs along the shores of the Pacific Ocean. The latter is, as it were, bordered by underwater mountain ranges, the peaks of which rise in the form of islands (Aleutian, Kuril, Japanese islands and others). Tsunami waves are generated here as a result of gaps between rising mountain ranges and deep-sea trenches that fall parallel to the ridges, separating island chains from the sedentary area of the Pacific Ocean floor.

The direct cause of the occurrence of tsunami waves is most often changes in the topography of the ocean floor that occur during earthquakes, leading to the formation of large faults, sinkholes, etc.

The scale of such changes can be judged from the following example. During an earthquake in the Adriatic Sea off the coast of Greece on October 26, 1873, ruptures were noted in the telegraph cable laid at the bottom of the sea at a depth of four hundred meters. After the earthquake, one of the ends of the broken cable was discovered at a depth of more than 600 m. Consequently, the earthquake caused a sharp subsidence of a section of the seabed to a depth of about 200 m. A few years later, as a result of another earthquake, the cable laid on a flat bottom again broke, and its ends found themselves at a depth that differed from the previous one by several hundred meters. Finally, another year after the new tremors, the sea depth at the rupture site increased by 400 m.

Even greater disturbances of the bottom topography occur during earthquakes in the Pacific Ocean. Thus, during an underwater earthquake in Sagami Bay (Japan), about 22.5 cubic meters were displaced when a section of the ocean floor suddenly rose. km of water, which hit the shore in the form of tsunami waves.

In Fig. Figure 2a shows the mechanism of tsunami generation as a result of an earthquake. At the moment of a sharp subsidence of a section of the ocean floor and the appearance of a depression on the seabed, the pod rushes to the center, overflows the depression and forms a huge bulge on the surface. When a section of the ocean floor rises sharply, significant masses of water are revealed. At the same time, tsunami waves arise on the surface of the ocean, quickly spreading in all directions. Usually they form a series of 3-9 waves, the distance between the crests of which is 100-300 km, and the height when the waves approach the shore reaches 30 m or more.

Another reason that causes tsunamis is volcanic eruptions that rise above the sea surface in the form of islands or are located on the ocean floor (Fig. 2b). The most striking example in this regard is the formation of a tsunami during the eruption of the Krakatoa volcano in the Sunda Strait in August 1883. The eruption was accompanied by the release of volcanic ash to a height of 30 km. The menacing voice of the volcano was heard simultaneously in Australia and on the nearest islands of Southeast Asia. On August 27 at 10 o'clock in the morning, a gigantic explosion destroyed the volcanic island. At this moment, tsunami waves arose, spreading across all oceans and devastating many islands of the Malay Archipelago. In the narrowest part of the Sunda Strait, the wave height reached 30-35 m. In some places, the water penetrated deep into Indonesia and caused terrible destruction. Four villages were destroyed on Sebezi Island. The cities of Angers, Merak and Bentham were destroyed, forests and railways were washed away, and fishing boats were abandoned on land several kilometers from the ocean shore. The shores of Sumatra and Java became unrecognizable - everything was covered with mud, ash, corpses of people and animals. This disaster brought the death of 36,000 inhabitants of the archipelago. Tsunami waves spread throughout the Indian Ocean from the coast of India in the north to the Cape of Good Hope in the south. In the Atlantic Ocean they reached the Isthmus of Panama, and in the Pacific Ocean they reached Alaska and San Francisco.

Cases of tsunamis during volcanic eruptions are also known in Japan. So, on September 23 and 24, 1952, there was a strong eruption of an underwater volcano on the Meijin Reef, several hundred kilometers from Tokyo. The resulting waves reached Hotidze Island, northeast of the volcano. During this disaster, the Japanese hydrographic vessel Kaiyo-Maru-5, from which observations were carried out, was lost.

The third reason for a tsunami is the fall of huge rock fragments into the sea, caused by the destruction of rocks by groundwater. The height of such waves depends on the mass of material that has fallen into the sea and the height of its fall. So, in 1930, on the island of Madeira, a block fell from a height of 200 m, which caused the appearance of a single wave 15 m high.

In Japanese, the character "tsu" means bay or bay, and "nami" means wave. Together, both hieroglyphs translate as “wave flooding the bay.” The catastrophic consequences of two tsunamis that hit the shores of the Indian Ocean in 2004 and Japan in 2011 clearly demonstrated that reliable protection against this formidable natural phenomenon has not yet been found...

Tsunami - what is it?

Contrary to popular belief, a tsunami is not one gigantic wave that suddenly hits the shore and sweeps away everything in its path. In fact, a tsunami is a series of marine gravity waves of very long length, resulting from the displacement of extended sections of the bottom during strong underwater earthquakes or, occasionally, for other reasons - as a result of volcanic eruptions, giant landslides, asteroid falls, underwater nuclear explosions.

How does a tsunami occur?

The most common cause of a tsunami is vertical movement of the bottom during underwater earthquakes. When part of the bottom sinks and part rises, the mass of water begins to oscillate. In this case, the water surface tends to return to its original level - the average ocean level - and thus generates a series of waves.

The speed of tsunami propagation at a sea depth of 4.5 km exceeds 800 km/h. But the wave height in the open sea is usually small - less than a meter, and the distance between the crests is several hundred kilometers, so a tsunami is not so easy to notice from the deck of a ship or from an airplane. In the vast oceans, encountering a tsunami is not dangerous for any ship. But when waves enter shallow water, their speed and length decrease, and their height increases sharply. Near the coast, the wave height often exceeds 10 m, and in exceptional cases reaches 30-40 m. Then the impact of the elements causes colossal damage to coastal cities.

However, tsunami waves of relatively low height often cause enormous destruction. At first glance, this seems strange: why don’t seemingly more formidable waves that arise during a storm lead to similar casualties? The fact is that the kinetic energy of a tsunami is much higher than that of wind waves: in the first case, the entire thickness of the water moves, and in the second, only the surface layer. As a result, the pressure of water splashing onto land during a tsunami is many times higher than during a storm.

One more factor should not be discounted. During a storm, the excitement increases gradually, and people usually manage to move to a safe distance before they begin to face danger. A tsunami always comes suddenly.

Today, about 1000 cases of tsunamis are known, of which more than a hundred had catastrophic consequences. Geographically, the periphery of the Pacific Ocean is considered the most dangerous region - approximately 80% of all tsunamis occur there.

It is impossible to completely protect the coast from a tsunami, although some countries, especially Japan, have tried to build breakwaters and breakwaters in order to reduce the force of the waves. However, there are cases when these structures played a negative role: tsunamis destroyed them, and pieces of concrete picked up by water flows only aggravated the damage on the shore. Hopes for protection from trees planted along the shore were also not realized. To dampen the energy of waves, too large an area of forest plantations is needed, and most coastal cities simply do not have that. Well, a narrow strip of trees along the embankment cannot provide any resistance to a tsunami.

One of the important measures to protect the population of dangerous regions from destructive waves was the international tsunami warning system created in the Pacific region. 25 states, including Russia, take part in its work. Scientists from different countries, based on a comprehensive analysis of strong earthquake zones, are trying to determine whether they caused tsunamis in the past, and what is the likelihood of tsunamis occurring in the future. The system's main research center, located in Honolulu, Hawaii, continuously monitors seismic conditions and surface levels in the Pacific Ocean.

In our country, the tsunami warning service of the Far East consists of three regional services: Kamchatka, Sakhalin regions and Primorsky Territory. In the Kamchatka region, in particular, there is a tsunami station of the territorial administration for hydrometeorology and environmental monitoring and a seismic station of the Institute of Earth Physics of the Russian Academy of Sciences.

The most destructive tsunamis of the past

It is possible that the most catastrophic tsunami event in human history occurred in ancient times, although it has come down to us in the form of myths and legends. Around 1450 BC. An entire civilization perished from a giant wave triggered by the Santorini volcano. 120 km from the volcano is Crete, which at that time was one of the most powerful powers in the Mediterranean. But the tsunami at one point caused colossal damage to the island of Crete, from which the previously prosperous state was never able to recover. It collapsed, and many of its cities were abandoned for two and a half thousand years.

Giant tsunami waves followed the devastating earthquake in Lisbon on November 1, 1755. The source of the earthquake was obviously at the bottom of the ocean. The total number of victims from the waves and earthquake is estimated at approximately 60 thousand people.

In 1883, as a result of a series of eruptions of the Krakatoa volcano in Indonesia, a powerful tsunami was formed, from which the islands of Java and Sumatra suffered the most. Waves up to 40 m high wiped out about 300 villages from the face of the earth, killing more than 36 thousand people. Near the city of Teluk Betung, a Dutch warship, the gunboat Berouw, was thrown 3 km inland and ended up on a mountainside at an altitude of 9 m above sea level. Seismic waves passed two or three times around the Earth, and unusual red dawns were observed for a long time in Europe from the ash thrown into the atmosphere.

The most destructive tsunami of the 20th century hit the coast of Chile on May 22, 1960. The tsunami and the powerful earthquake that generated it, measuring 9.5 on the Richter scale, killed 2,000 people, injured 3,000, left two million homeless, and caused $550 million in damage. The same tsunami killed 61 people in Hawaii, 20 in the Philippines, 3 in Okinawa and more than 100 in Japan. The wave height on Pitcairn Island reached 13 m, on Hawaii - 12 m.

The most unusual tsunami

In 1958, a tsunami was generated in Lituya Bay, Alaska, caused by a giant landslide - about 81 million tons of ice and solid rock fell into the sea as a result of the earthquake. The waves reached an incredible height of 350-500 m - these are the largest waves ever recorded in history! The tsunami washed away all vegetation from the mountain slopes. Fortunately, the shores of the bay were uninhabited, and human casualties were minimal - only two fishermen died.

Tsunami in the Russian Far East

On April 4, 1923, a strong earthquake occurred in the Kamchatka Bay. 15-20 minutes later a wave approached the top of the bay. Two fish factories on the coast were completely destroyed, and the village of Ust-Kamchatsk was severely damaged. The ice on the Kamchatka River was broken over a distance of 7 km. 50 km southwest of the village, the maximum height of water rise on the coast was observed - up to 30 m.

On Russian territory, the most catastrophic tsunami occurred on the night of November 4–5, 1952, on the Far Eastern island of Paramushir, where the city of Severo-Kurilsk is located. At about 4 a.m., strong tremors began. Half an hour later the earthquake stopped, and the people who had left their homes returned to their homes. Only a few remained outside and noticed the approaching wave. They managed to take refuge in the hills, but when they went down to inspect the destruction and look for relatives, a second, even more powerful wave of water about 15 m high fell on the city. The captain of one tug stationed in the roadstead of Severo-Kurilsk said that that night the sailors did nothing They didn’t notice, but early in the morning they were surprised by the large amount of garbage and various objects floating around. When the morning fog cleared, they saw that there was no city on the shore.

On the same day, the tsunami reached the shores of Kamchatka and caused serious damage to a number of villages. In total, more than 2,000 people died, but in the USSR, until the early 1990s, almost no one knew about the events of that tragic night.

The tsunami that occurred on May 23, 1960, off the coast of Chile, reached the shores of the Kuril Islands and Kamchatka about a day later. The highest level of water rise was 6-7 m, and on the territory of the Khalaktyrsky beach near Petropavlovsk-Kamchatsky - 15 m. In Vilyuchinskaya and Russkaya bays, houses were destroyed and outbuildings were washed into the sea.

The spread of the tsunami in the Pacific Ocean (the most destructive waves are black and red) after the 1960 earthquake. Map prepared by the US National Oceanic and Atmospheric Administration (NOAA)

Indian Ocean disaster (2004)

After an earthquake measuring about 9 on the Richter scale with an epicenter in the northern part of the island of Sumatra in Indonesia, which occurred on the night of December 26, 2004, a powerful tsunami covered the Indian Ocean. The more than 1,000-kilometer fault line, created by the movement of large layers of the earth's crust on the ocean floor, generated a huge release of energy. The waves hit Indonesia, Sri Lanka, India, Malaysia, Thailand, Bangladesh, Myanmar, the Maldives and Seychelles and reached Somalia, located 5 thousand km from the epicenter of the earthquake. More than 300 thousand people became victims of the tsunami, including foreign tourists from many countries who were vacationing in Indonesia and Thailand in those days. Most of the dead were in Indonesia (more than 180 thousand) and Sri Lanka (about 39 thousand).

Such numerous casualties are largely explained by the lack of basic knowledge among the local population about the impending danger. So, when the sea retreated from the shore, many locals and tourists remained on the shore - out of curiosity or out of a desire to collect the fish remaining in the puddles. In addition, after the first wave, many returned to their homes to assess the damage or try to find loved ones, not knowing that others would follow the first wave.

Tsunami in Japan (2011)

The cause of the tsunami was a strong earthquake of magnitude 9.0-9.1 that occurred on March 11, 2011 at 14:46 local time (8:46 Moscow time). The center of the earthquake was at a depth of 32 km, at a point with coordinates 38.322° N. 142.369°E east of the island of Honshu, 130 km east of the city of Sendai and 373 km northeast of Tokyo. In Japan, the tsunami caused widespread destruction on the east coast. The maximum wave height was observed in Miyagi Prefecture - 10 m. The tsunami flooded the Sendai airport, washed away one passenger train, and caused serious damage to the Fukushima I nuclear power plant. In Sendai alone, the tsunami caused the death of approximately 300 people. The total damage caused to the country's economy amounts to hundreds of billions of dollars.

According to official data, the death toll from the earthquake and tsunami was 15,892 people, with another 2,576 people listed as missing. 6,152 people were seriously injured. According to unofficial data, the number of victims is much higher. According to media reports, 9,500 people are missing in the city of Minamisanriku alone.

Numerous photographic documents paint a truly apocalyptic picture of destruction:

The tsunami was observed along the entire Pacific coast - from Alaska to Chile, but outside Japan it looked much weaker. Hawaii's tourism infrastructure was hit the hardest—about 200 private yachts and boats were wrecked and sunk in Honolulu alone. On the island of Guam, waves tore two US Navy nuclear submarines from their moorings. In Crescent City, California, more than 30 boats and boats were damaged and one person was killed.

According to the Russian Ministry of Emergency Situations, due to the threat of a tsunami on the Kuril Islands, 11 thousand residents were evacuated from coastal areas. The highest wave height - about 3 m - was recorded in the area of the village of Malokurilskoye.

Tsunami in cinema

In the popular genre of disaster films, tsunamis have repeatedly attracted the attention of screenwriters and directors. An example is the feature film “Tsunami” (South Korea, 2009), frames from which are given below.

Plan:

Causes of tsunamis
Tsunami off the coast of South America
Tsunami off the coast of Japan
Tsunami off the Pacific coast of Russia
Tsunami in Hawaii
Application
Literature

Causes of tsunamis

The direct cause of the occurrence of tsunami waves is most often changes in the topography of the ocean floor that occur during earthquakes, leading to the formation of large faults, sinkholes, etc.

In Fig. Figure 2a shows the mechanism of tsunami generation as a result of an earthquake. At the moment of a sharp subsidence of a section of the ocean floor and the appearance of a depression on the seabed, the pod rushes to the center, overflows the depression and forms a huge bulge on the surface. When a section of the ocean floor rises sharply, significant masses of water are revealed. At the same time, tsunami waves arise on the surface of the ocean, quickly spreading in all directions. They usually form a series of 3–9 waves, the distance between the crests of which is 100–300 km, and the height when the waves approach the shore reaches 30 m or more.

Another reason that causes a tsunami is the eruption of volcanoes that rise above the sea surface in the form of islands or located on the ocean floor (Fig. 2b). The most striking example in this regard is the formation of a tsunami during the eruption of the Krakatoa volcano in the Sunda Strait in August 1883. The eruption was accompanied by the release of volcanic ash to a height of 30 km. The menacing voice of the volcano was heard simultaneously in Australia and on the nearest islands of Southeast Asia. On August 27 at 10 o'clock in the morning, a gigantic explosion destroyed the volcanic island. At this moment, tsunami waves arose, spreading across all oceans and devastating many islands of the Malay Archipelago. In the narrowest part of the Sunda Strait, the wave height reached 30–35 m. In some places, the waters penetrated deep into Indonesia and caused terrible destruction. Four villages were destroyed on Sebezi Island. The cities of Angers, Merak and Bentham were destroyed, forests and railways were washed away, and fishing boats were abandoned on land several kilometers from the ocean shore. The shores of Sumatra and Java became unrecognizable - everything was covered with mud, ash, corpses of people and animals. This disaster brought the death of 36,000 inhabitants of the archipelago. Tsunami waves spread throughout the Indian Ocean from the coast of India in the north to the Cape of Good Hope in the south. In the Atlantic Ocean they reached the Isthmus of Panama, and in the Pacific Ocean they reached Alaska and San Francisco.

Tsunami off the coast of South America

The Pacific coast within Peru and Chile is subject to frequent earthquakes. Changes occurring in the bottom topography of the coastal part of the Pacific Ocean lead to the formation of large tsunamis. The tsunami waves reached their highest height (27 m) in the Callao area during the Lima earthquake in 1746.

If usually the decrease in sea level that precedes the onset of tsunami waves on the coast lasts from 5 to 35 minutes, then during the earthquake in Pisco (Peru) the receding sea waters returned only after three hours, and in Santa even after a day.

Often the onset and retreat of tsunami waves occur here several times in a row. Thus, in Iquique (Peru) on May 9, 1877, the first wave hit the coast half an hour after the main shock of the earthquake, and then within four hours the waves arrived five more times. During this earthquake, the epicenter of which was located 90 km from the Peruvian coast, tsunami waves reached the coasts of New Zealand and Japan.

On August 13, 1868, on the coast of Peru in Arica, 20 minutes after the earthquake began, a wave several meters high surged, but soon receded. With an interval of a quarter of an hour, it was followed by several more waves, smaller in size. After 12.5 hours, the first wave reached the Hawaiian Islands, and 19 hours later - the coast of New Zealand, where 25,000 people became victims. The average speed of tsunami waves between Arica and Valdivia at a depth of 2200 m was 145 m/sec, between Arica and Hawaii at a depth of 5200 m – 170-220 m/sec, and between Arica and the Chatham Islands at a depth of 2700 m – 160 m/sec.

Over the past decade, the number of natural disasters around the globe has more than doubled. The most dangerous natural phenomena include tsunamis - huge killer waves.

Do you think you know enough about this? Then try answering these simple questions:

list the signs by which one can determine its approach;
tell us what needs to be done to avoid being harmed by the rogue wave.

Didn't work out? Then read this article carefully, perhaps this information will one day help save your life.

What is a tsunami?

We will talk about a tsunami - the causes and consequences of this phenomenon should be known to modern society. The well-known term came to us from Japan and it is not surprising because it is this country that most often suffers from rogue waves. denoted by two hieroglyphs: 津 - “bay, port, bay” and 波 - “wave”. Therefore, in direct translation, this word means “wave in the bay.” These are huge waves that originate in the depths of the ocean and crash onto the shore with enormous destructive force.

The damaging factors of a tsunami can be defined as primary and secondary. The primary ones include:

wave blow;
air wave preceding flooding;
hydrodynamic pressure;
secondary ones are:
complete flooding of the area;
beaching of ships;
destruction of buildings, roads, bridges, power lines and other objects in the path of the wave;
the death of all living things;
soil erosion, destruction of agricultural plantings;
fires.

Where does this phenomenon most often occur?

The causes of tsunamis are most often associated with geological activity. Most likely, a similar phenomenon can be found on the Pacific coast. This is primarily due to the high geoactivity of this basin. Over the past millennium, these areas have been hit by rogue waves more than 1,000 times. At the same time, in the Indian and Atlantic Oceans, this phenomenon was observed several times less frequently.

On the territory of Russia, the most dangerous, from the point of view of tsunami occurrence, are the coasts of the Kuril Islands and Kamchatka, as well as the island of Sakhalin.

Rogue Wave Parameters

When considering the causes of a tsunami, it is worth first of all to talk about what parameters characterize such waves and how they can be measured. Like any other wave, a tsunami has a length, height and speed of movement.

The wavelength is the horizontal distance between two peaks (crests) of adjacent waves. The average length of a rogue wave can range from 150 to 300 km.
The height is the distance between the crest and the bottom of one wave. Above the center of the tsunami, this figure can be quite small - from 1 to 5 meters.
Speed is the linear speed of movement of a specific element, for example, a comb. Most often, this figure ranges from 500 to 1000 km/h, which, you see, is a lot.

All indicators of a tsunami wave depend on the depth of the origin. The deeper the wave originates, the greater its length and the higher the speed of propagation, but the height will be just small. For example, the speed of tsunami propagation in the Pacific Ocean, whose average depth is about 4 km, is approximately 700-800 km/h. When approaching the coastline, the speed of wave propagation sharply decreases to 80-100 km/h. Thus, the shallower the depth, the shorter the waves, but the height increases sharply when approaching the shore. In some cases it can reach 45-50 meters.

Intensity

Before we talk about what causes a tsunami, let's consider the intensity parameters of this phenomenon. Yes, yes, a tsunami, like an earthquake, has a division expressed in points. There are six levels in total and they mean the following:

1 point - the phenomenon is very weakly expressed, such a tsunami can only be recorded by special instruments - seaographers;
2 points - a rather weak wave that can only flood a flat coast; it can also be noticed mainly by specialists;
3 points - a tsunami of medium power, anyone can notice it; it is characterized by flooding of the flat coast and slight destruction of coastal buildings; light craft may also be thrown ashore;
4 points - a fairly severe natural disaster; the coast is completely flooded, and all coastal buildings are significantly damaged; light motor vessels and fairly large sailboats were washed ashore and then washed back; the coastline is littered with sand, silt and tree debris; human casualties are also likely;
5 points - a very strong phenomenon, accompanied by numerous casualties; the coastline has been severely destroyed for many hundreds of meters, large ships have been thrown ashore; nearby rivers overflow their banks from a strong storm surge;
6 points - catastrophic consequences; the land is completely flooded many kilometers deep, there are massive casualties, and complete devastation of the surrounding areas is observed.

What causes killer waves?

So we come to the question of why these terrible waves arise. To begin with, let us briefly list the causes of a tsunami:

landslides;
earthquakes;
volcanic eruptions;
meteorite falls;
human activity.

The main cause of a rogue wave is an underwater earthquake with a sharp rise or fall in the level of the seabed. About 85% of all tsunamis occur for this reason. But not every underwater earthquake is accompanied by the appearance of a huge wave. Most often this happens when the lesion is not too deep.

Another reason is landslides. They account for about 7-8% of the elements. This reason for the occurrence of storm waves and tsunamis is, as it were, secondary, since landslides most often occur as a result of earthquakes.

The third reason is underwater volcanic eruptions. Large underwater eruptions have much the same effect as earthquakes. The largest and most famous eruption occurred in 1883. caused a huge tsunami that destroyed more than 5,000 ships, killing about 36,000 people worldwide.

The rapidly developing nuclear energy industry has created the preconditions for the emergence of another reason for the appearance of giant waves - human activity. Various deep-sea tests, for example, atomic explosions, can also cause a phenomenon such as a tsunami.

A very small, but still percentage, is given to cosmic phenomena, for example, the fall of meteorites.

It is worth noting that giant waves are most often the result of not one, but a number of factors. And in this case they are especially destructive. These may be the main causes of a tsunami.

Consequences

One of the most terrible consequences of a tsunami, of course, is human casualties. Even one life of a person buried by a wave is already a huge grief. What can we say about the hundreds and thousands of dead.

In addition, tsunamis cause salinization and erosion of large areas of the coast, as well as complete flooding of coastal areas. All ships moored near the shore are destroyed, and nearby buildings and structures can be destroyed to the ground.

How to recognize an approaching tsunami?

The causes of a tsunami are more or less clear, but how to recognize the signs that portend trouble?

Birds and animals are usually the first to sense the approach and begin to leave their homes. A massive “relocation” of animals can begin either a few hours or a few days before the disaster. Probably, birds and animals feel certain energy waves sent by Mother Earth. In fact, animals are affected by an electromagnetic field: a whole stream of charged ions rises from the surface of the earth into the atmosphere, charging the air to the limit with electricity. By the way, not only animals feel this phenomenon - many so-called weather-dependent people begin to have unbearable headaches.

If you live on the coast, get yourself an aquarium and carefully observe its inhabitants. This is exactly what the Japanese do, who for many decades have been determining the approach of seismic activity by the behavior of aquarium catfish. In anticipation of shocks, these fish behave very restlessly, literally trying to jump out of the aquarium.

Clear signs of an approaching tsunami may look like this:

the water quickly and suddenly moves away from the shore, leaving a wide strip of sand;
there are signs of a small (or strong) earthquake, although this point is not at all necessary, since the epicenter of the earthquake may be located far in the ocean and not be felt at all on the shore;
the movement of the waves is accompanied by sounds similar to thunder;
changes in the behavior of animals, birds and fish (they can wash ashore).

What should you do if you notice a wave approaching?

If you notice the causes of a tsunami, such as an earthquake or a meteorite, or see clear signs of its approach, you should not hesitate for a second. Take your most valuable things and documents with you, take your children and elderly relatives and leave the coast inland as quickly as possible. Agree on a meeting place with your family in advance in case you lose each other.

If it is not possible to quickly leave a dangerous place, look for other ways to escape. It could be some kind of natural elevation - a mountain or a hillock. Tall permanent buildings made of stone or concrete are also suitable. It is best if they are located at least a little further from the shore.

You need to move along the shortest route, avoiding river banks and various water bodies - bridges, dams, reservoirs. A distance of at least 3-5 km from the coastline can be considered safe.

Try to remain calm - panic only gets in the way. The occurrence of a tsunami is usually detected by instruments and turned on. Never ignore these sounds, even if several times it turns out that the alarm is false.

Never stay to watch a tsunami or go close to the shore for 3-4 hours after the first wave arrives. The fact is that there is rarely only one wave - the second, or even the third can come in 30 minutes or even in 3 hours. Make sure it's all over before you return.

Knowing these simple rules can truly save your life. Follow them whenever you notice the first signs of a rogue wave approaching. Do not ignore the sounds of the siren even if everyone around you assures you that it is a false alarm.

Conclusion

Now you know exactly the causes of a tsunami and their possible consequences. I would like this knowledge to really help in a difficult situation. Remember, a tsunami is a very fast and extremely dangerous natural disaster. Knowing the causes of this phenomenon and basic rules of behavior can really save your life.